Boilers for electric power generation often have combustion systems with furnaces that are fired with solid fuel, such as bituminous coal, lignite, biomass, etc.; these combustion systems are usually provided with mills and ducting for supplying the pulverized fuel to one or more burners. Generally, during the combustion process of fossil fuels pollutants such as nitrogen oxides (NOx) and sulfur oxides (SO2 and SO3) are generated. If allowed to enter the atmosphere, these pollutants can detrimentally impact the environment and pose health hazards to humans and animals. U.S. Pat. No. 8,017,084 discloses an ammonia injection grid for a selective catalytic reduction (SCR) system that provides uniform distribution of ammonia to the SCR catalyst in NOx reduction systems for heat recovery steam generation systems, packaged boilers, simple cycle catalyst systems, utility boilers and fired heaters for superior operational efficiency. The ammonia injection grid includes an injection tube nozzle for injecting ammonia into a flow of flue gas. The ammonia injection grid also includes a corrugated turbulence enhancer associated with the injection tube to generate turbulent wake to enhance turbulent mixing.
State-of-the-art grid arrangements have two independent injection grids for reducing NOx and controlling SO3 emissions. These grid arrangements having separate grids imply a large consumption of chemicals as such chemicals are distributed separately in the furnace/boiler and thus large cost associated with the chemicals. Further such independent grid arrangements take a lot more space along with separate auxiliaries for each grid which leads to a more complex working arrangement with high capital cost of multi-additive systems with multiple control systems. Each grid arrangement is controlled separately to supply chemicals for reducing NOx and controlling SO3 emissions leading to a more complex arrangement with multiple controls.
Consequently, there is need to provide a grid arrangement which is simple in operation, easy in installation, less expensive in capital cost and more effective in reducing NOx and controlling SO3 emissions at various locations in the furnace/boiler.